Process of making cyanoalkylsilanes



hit t 3,020,301 PRGCESS F MAKTNG CYANQALKYLSHANEd Roscoe A. Pike, Grand island, N.Y., assignor to Union Carbide Corporation, a corporation of New York No Drawing. Filed Dec. 30, 1959, er. No. 862,749 6 Claims. (Cl. 26i)448.2)

This invention is directed to a process for making cyanoalkylsilanes containing three hydrolyzable groups attached to silicon and a cyano group interconnected to silicon through at least two carbon atoms of an alkyl group of two or more carbon atoms. More particularly, this invention relates to a process involving the reaction of alkene nitriles with silanes having hydrogen and three hydrolyzable groups attached to silicon in the presence of a morpholinosilane catalyst.

It has heretofore been shown that when an acrylonitrile is reacted with a silane having a silanic hydrogen the silyl group of the silane bonds to that carbon atom of the two olefinic carbon atoms which is interconnected to the cyano group through the lesser number of carbon atoms and the silanic hydrogen bonds to that carbon atom of the two olefinic carbon atoms which is interconnected ,to cyano group through the greater number of carbon atoms. The reaction taking place, for example, between acrylonitrile and trichlorosilane, is represented by the equation:

H2O=CHON+HSiCl3- HgCCHCN III SiCls CHz-CHz At- Sl N CH CH y wherein A is a monovalent hydrocarbon group, a halogen atom or an alkoxy group and y is an integer of 1 to 4. Thus, included are the morpholinotrialkylsilanes, the morpholinotrihalosilanes and the morpholinotrialkoxysilanes as represented by the above formula where A is, respectively, alkyl, halogen and alkoxy and y is l. EX- amples of these morpholinosilanes are (CH SiNC H O, 2 4 s )2, z 5 4 s )a 4 8 )4 and the like. Methods for preparing these silanes are known in the art. In general they are prepared by reacting a silane having at least one silicon-bonded halogen atom with preferably at least two moles of morpholine for each silicon-bonded halogen desired to be displaced, in a solvent, such as petroleum ether or isopropyl ether, at atmospheric pressure and room temperature. Cooling, as by an ice bath, is employed when the temperature of reaction increases much above room temperature. This reaction forms the morhpolinosilane and a morpholine hydrohalide. The morpholinosilanes are isolated by filtering out the morpholine hydrohalide and distillation of the resulting filtrate through a packed column.

In carrying out the process of this invention the silyl group of the silane starting materials bonds to that carbon atom of the two olefinic carbon atoms of the alkene nitrile starting material which is interconnected to the cyano group through the greaterjnumber of carbon atoms and the silanic hydrogen atom of the silane starting material bonds to that carbon atom of the two olefinic carbon atoms of the nitrile starting material which is interconnected to the cyano group through the lesser number of carbon atoms. The reaction taking place is represented by the following equation wherein acrylonitrile is employed as exemplifying the alkene nitrile starting material 3,92%,351 Patented Feb. 6, 1962 and HSiX (X being a hydrolyzable group) represents the silane starting material:

The process is carried out by forming a mixture of the alkene nitrile, the silane (HSiX and the morpholinosilane catalyst and heating the mixture to a temperature sufficiently elevated to bring about reaction of the nitrile and silane. When either one or both of the starting materials are gaseous at the reaction temperature a closed system, in accordance with techniques commonly employed in the art to maintain the concentrations of the starting materials at suficient levels for providing the intimate reactive contact necessary for reaction, can be used. The process is advantageously carried out in pressure vessels or bombs in order to vfacilitate observation and favor closer control of reaction conditions, particularly when the one or both of the starting materials is gaseous at the reaction temperature. Continuous process systems can also be employed in carrying out the process.

Catalyst concentration is not narrowly critical and can be varied over a wide range. Thus, as little as 0.5 weight percent and as much as 10 weight percent of catalyst based on the combined weights of the starting materials are advantageously employed. Catalyst concentrations outside of this range are operable in the process but do not provide any additional advantage. A preferable catalyst concentration range has been found to be 1.6 to 2.5 weight percent based on the combined weights of the starting materials.

Equimolar or stoichiometric amounts of the starting materials have been found to be entirely suitable in the process. An excess of one or the other starting material over the stoichiometric amount can also be employed but no commensurate gain is obtained thereby. A useful range of amounts of starting materials is about one-half to two moles of the alkene nitrile per mole of the silane.

The temperatures employed in the process can be varied over a wide range from 50 C. to 250 C. Temperatures outside this range can be employed, if desired,

but to no noticeable advantage. Within this temperature range reaction times vary from one-half to ten hours. Reaction times of one to about three hours are advantageously used when the process is conducted at temperatures in the range of C. to C.

The mixture resulting after completion of the reaction contains the cyanoalkylsilane product, some unreacted nitrile and silane starting materials and other materials mainly believed to be polymeric substances. The cyanoalkylsilane product is advantageously recovered from this mixture by fractional distillation, preferably under reduced pressure. Other means of recovery are within the skill of workers in the art and can be employed. When fractional distillation is employed for recovery, the cyanoalkylsilane product is obtained as a cut or series of cuts at its characteristic boiling point under the distillation pressure employed. Other high boiling materials such as, unreacted starting materials are removed as a series of cuts and a residue or heavies remain in the still pot. These heavies are believed to be various polymerization materials of the alkene nitrile and the silane starting material and represent a loss of starting mate rial. It has been found that the amount of heavies resulting from the process can be greatly reduced by adding to the initial reaction mixture difunctional silanes of the formula RSlHX .(X being a hydrolyzable group and R being a monovalent hydrocarbon group). These diploying such difunctional silanes and longer reaction timcsor higher temperatures or, alternatively, the starting materials saved from polymerizing can be recovered and reused to provide a substantial economy. A polymerization inhibitor known in the art to inhibit the polymerization of the alkene nitrile also can be used and thus reduce the amount of heavies obtained. Such polymerization inhibitors are 2,t-di-tertiary butylparacresol, hydroquinone, t-butylcatachol, t-buty1-4-methylphenol and the like. 7

The alkene nitriles used as starting materials in the process are known in the art. The alkene nitriles are represented by the formula, alkenyl-CN, and include acrylonitrile, methacrylonitrile, crotononitrile, allyl cyanide, methallyl cyanide, 1-cyano-4-pentene, l-cyano-3- butene, l-cyano-l-hexene and the like.

The silane starting materials are also known and are represented by the formula:

HSiX

wherein X represents a hydrolyzable group including alkoxy, aryloxy, acetoXy, halogen and the like. Preferred silane starting materials are the halosilanes and alkoxysilanes as shown by the formula wherein X is halogen or alkoxy. Illustrative of these silanes are trichlorohydrogensilane, triethoxyhydrogensilane, triacetoxyhydrogensilane, triphenoxyhydrogensilane and the like.

The cyanoalkylsilane products made by the process are represented by the formula:

NC(C H SiX where X is as previously defined, C,,H is a divalent alkane group, a is an integer of at least 2 and NC- is interconnected to silicon through at least two carbon atoms of the divalent alkane group, C H Such cyanoalkylsilanes are illustrated by beta-cyanoethyltrichlorosilane, beta-cyanoethyltriethoxysilane, gamma-cyanopropyltrichlorosilane, beta-cyanopropyltriethoxysilane and the like. These cyanoalkylsilane products are useful in a variety of applications. They can be hydrolyzed and condensed to provide quick-curing resins useful in the manufacture of molded articles, protective coatings and laminates. The cyanoalkylchlorosilane products can be esterified with alkanols to provide the corresponding cyanoalkylalkoxysilanes which can be hydrogenated to give the corresponding aminoalkylalkoxysilanes. The aminoalkylalkoxysilanes are particularly useful as protective coatings for metal articles when applied to and cured on the surface of such articles.

One particular advantage of the use of morpholinosilane catalysts in accordance with this invention is the ease with which catalyst contamination of the product can be avoided. The morpholinosilanes employed as catalysts herein are easily removed by esterification with an alcohol or by hydrolysis to convert the morpholinosilane into a low boiling silylalkoxide or silanol by cleavage of the Si-N bond and stripping the low boiling material from the product. In many applications the removal of the morpholinosilane catalyst is accomplished during the use of the cyanoalkyls lanes and no additional steps need be taken for catalyst removal. For example, when esterifying cyanoalkylchlorosilanes to the corresponding cyanoalkylalkoxysilanes the morpholinosilane catalyst is removed in the ordinary course of the esterification. In many other applications the presence of the morpholinosilane catalyst in the cyanoalkylsilane products is not at all objectionable.

The following example is presented. In this example, 1 weight percent of Ionol (a hindered phenol designated as 2,6-di-tertiary-butyl-4-methyl phenol) based on the combined weight of acrylonitrile and trichlorosilane was added to the reaction mixture to inhibit the polymerization of acrylonitrile. Although hindered phenols have previously been shown to catalyze the reaction of Into a 300 cubic centimeter stainless steel pressure vessel were charged acrylonitrile and trichlorosilane (HSiCl in a one to one molar ratio, 1 weight percent of 101101 and 2 weight percent of morpholinotrimethylsilane,

CH2CHg (OHahSiN GE -CH2 weight percents being based on combined weights of acrylonitrile and trichlorosilane. The vessel was sealed and heated in a rocking furnace at 150 C. for one hour. After one hour at 150 C. the vessel was cooled and discharged of its liquid contents. The liquid contents were distilled through a Vigreaux column to give 36.4 weight percent of beta-cyanoethyltrichlorosilane based on the combined weights of acrylonitrile and trichlorosilane originally charged and 13.8 weight percent of heavies on the same weight basis.

In a procedure similar to that described in the example the following morpholinosilane catalysts can be employed as catalysts in reacting trichlorosilane with acrylonitrile to produce beta-cyanoethyltrichlorosilane in high yields:

Dimorpholinodiethylsilane, Trimorpholinophenylsilane, Morpholinotrichlorosilane, Dimorpholinodiethoxysilane, and Morpholinophenyldichlorosilane.

ca om Ai si N/ /0 UHF-CH2 where A is selected from the class consisting of alkyl 7 groups, phenyl groups, a halogen atomand an alkoxy group and y is an integer from 1 to 4.

2. A process as claimed in claim 1 wherein the alkene nitrile is acrylonitrile and the silane is trichlorosilane.

3. A process as claimed in claim 1 wherein the catalyst is a morpholinotrialkylsilane.

4. A process as claimed in claim 1 wherein the catalyst is a morpholinotrihalosilane.

. 5. A process as claimed in claim 1 wherein the catalyst is a morpholinotrialkoxysilane.

6. A process for preparing beta-cyanoethyltrichlorosilane which comprises reacting acrylonitrile with trichlorosilane in the presence of morpholinotrimethylsilane.

References Cited in the file of this patent UNITED STATES PATENTS 2,716,638 Cohen et al Aug. 30, 1955 FOREIGN PATENTS 1,118,500 France Mar. 19, 1956 

1. A PROCESS FOR PREPARING A CYANOALKYLSILANE WHEREIN THE CYANO GROUP IS INTERCONNECTED TO SILICON THROUGH AT LEAST TWO CARBON ATOMS, WHICH COMPRISES REACTING AN ALKENE NUTRILE WITH A SILANE HAVING ONE SILICON-BONDED HYDROGEN AND THREE SILICON-BONDED HYDROLYZABLE GROUPS SELECTED FROM THE CLASS CONSISTING OF ALKOXY GROUPS, ARYLOXY GROUPS, ACETOXY GROUPS AND HALOGEN IN THE PRESENCE OF A MORPHOLINOSILANS CATALYST OF THE FORMULA: 